More objc gc work. Match gcc's treatment of ivar access

true a local pointer to objective-c object in generating
write barriers.

llvm-svn: 65290

clang/include/clang/AST/Expr.h

@@ -238,6 +238,10 @@ public:
   /// duration.  This means that the address of this expression is a link-time
   /// constant.
   bool hasGlobalStorage() const;  
+
+  /// isOBJCGCCandidate - Return true if this expression may be used in a read/
+  /// write barrier. 
+  bool isOBJCGCCandidate() const;
   
   /// IgnoreParens - Ignore parentheses.  If this Expr is a ParenExpr, return
   ///  its subexpression.  If that subexpression is also a ParenExpr, 

clang/lib/AST/Expr.cpp

@@ -745,6 +745,33 @@ bool Expr::hasGlobalStorage() const {
   }
 }
 
+/// isOBJCGCCandidate - Check if an expression is objc gc'able.
+///
+bool Expr::isOBJCGCCandidate() const {
+  switch (getStmtClass()) {
+  default:
+    return false;
+  case ObjCIvarRefExprClass:
+    return true;
+  case ParenExprClass:
+    return cast<ParenExpr>(this)->getSubExpr()->isOBJCGCCandidate();
+  case ImplicitCastExprClass:
+    return cast<ImplicitCastExpr>(this)->getSubExpr()->isOBJCGCCandidate();
+  case DeclRefExprClass:
+  case QualifiedDeclRefExprClass: {
+    const Decl *D = cast<DeclRefExpr>(this)->getDecl();
+    if (const VarDecl *VD = dyn_cast<VarDecl>(D))
+      return VD->hasGlobalStorage();
+    return false;
+  }
+  case MemberExprClass: {
+    const MemberExpr *M = cast<MemberExpr>(this);
+    return !M->isArrow() && M->getBase()->isOBJCGCCandidate();
+  }
+  case ArraySubscriptExprClass:
+    return cast<ArraySubscriptExpr>(this)->getBase()->isOBJCGCCandidate();
+  }
+}
 Expr* Expr::IgnoreParens() {
   Expr* E = this;
   while (ParenExpr* P = dyn_cast<ParenExpr>(E))

clang/lib/CodeGen/CGExpr.cpp

@@ -782,7 +782,7 @@ LValue CodeGenFunction::EmitArraySubscriptExpr(const ArraySubscriptExpr *E) {
            getContext().getObjCGCAttrKind(T));
   if (getContext().getLangOptions().ObjC1 &&
       getContext().getLangOptions().getGCMode() != LangOptions::NonGC)
-    LValue::SetObjCNonGC(LV, !E->hasGlobalStorage());
+    LValue::SetObjCNonGC(LV, !E->isOBJCGCCandidate());
   return LV;
 }